Critics: Nuclear Utilities Gloss Over Risks

The meltdown at the Chernobyl nuclear power plant has renewed criticism about atomic energy, despite claims by industry experts that such an accident could never happen in the United States.

Utility officials in Florida and elsewhere say the lack of a concrete and steel containment wall around the Soviet reactor allowed radiation to escape uncontrolled and spread across Eastern Europe. Containment walls are required in the United States.

But critics contend that utilities are misleading the public about the effectiveness of containment walls and minimizing the potential for a nuclear disaster in this country.

''Containment walls are not designed or able to withstand a major meltdown, although they offer protection for a wide range of other accidents,'' said Robert Pollard, a nuclear safety engineer with the Union of Concern Scientists in Washington. He supervised safety evaluations of nuclear plants for the Nuclear Regulatory Commission from 1970-76.

Although little official information on the Chernobyl accident is available, some U.S. industry experts believe the graphite bricks used to control the chain reaction in that plant might have caught fire during a routine heating process designed to realign them.

''After a while, the bricks become warped by heat and the bombardment of radiation,'' said Scott Peters, an energy analyst with the Atomic Industrial Forum, an industry association in Bethesda, Md.

''The way to cure this is to superheat the graphite, which realigns the crystal.''

In the process, water used to cool the reactor might have boiled dry, sending the reactor temperature soaring above 5,000 degrees Fahrenheit. Without a containment building, radiation was released into the environment as soon as the molten fuel burned through the reactor vessel.

In the Three Mile Island nuclear power accident in Harrisburg, Pa., in March 1979, the fuel melted through the vessel but was cooled off before it could eat through the concrete containment building, he said.

Pollard said, however, a 1985 NRC study, prompted by the radioactive fuel spill at Three Mile Island, showed that industry and government experts had overestimated the effectiveness of the containment walls under severe conditions.

NRC spokeswoman Ann Overton said the containment building is part of a required safety network, which works to prevent a nuclear power accident or limit damage in the event of one.

''After TMI there were a lot more post-accident systems required and we have two inspectors at every plant to make daily or weekly checks,'' she said. Florida's five nuclear reactors, like nearly all of the nation's 101 atomic generators, are surrounded by several physical barriers and connected to sensitive monitoring devices, said spokesmen with Florida Power & Light Co. and Florida Power Corp.

FPL, which has 1.5 million customers statewide, owns four nuclear units, two at Turkey Point near Miami and two in St. Lucie County. Florida Power, with 950,000 customers, has a nuclear unit at its Crystal River site in Citrus County.

''There are a series of physical barriers to prevent the release of large quantities of reactive materials during normal and accident type conditions,'' said FPL spokesman Carl Pounds.

The first layer of protection is applied to the uranium, which is packed in dense ceramic pellets. The pellets are placed in fuel rods made of a metal alloy. The fuel rods are bundled with boron rods, used to stop the the breakdown of uranium into energy when needed. The rods are then placed in a metal vessel filled with water. The vessel thickness at Florida plants varies from 4.74 inches to 9 inches.

A steel-reinforced concrete containment building is constructed around the vessel, with walls about 3.5 feet thick and a foundation of up to 16 feet.

Except for the containment structure, Soviet and U.S. plants have similar safety systems, Pollard said. Like U.S. plants, Soviet reactors are encased in a metal vessel and connected to monitoring systems.

The other difference is the use of graphite instead of water to slow the breakdown of uranium atoms into neutrons. The clash of neutrons produces heat, which boils water into steam. The steam drives a turbogenerator, which makes electricity.

''The Soviet plants without containment are as safe as the nuclear plants here,'' Pollard said.

What is disturbing is the NRC's tolerance of safety-related problems at U.S. plants, he said.

''The U.S. people must demand that the NRC stop the practice of allowing nuclear plants to operate with known problems,'' Pollard said.

Florida Power's Crystal River plant and four others built by Babcock & Wilcox Inc. in Lynchburg, Va., have repeatedly gone off line because of safety-related problems, but the NRC refuses to stop their operating, Pollard said.

Three Mile Island also was built by the company.

Since it opened nine years ago, Crystal River has shut down 32 times for safety-related problems with radioactive leaks and malfunctions of reactor coolant pumps.